In a public switched telephone network (PSTN), a telephone line made of a pair of wires (typically copper) runs from a telephone exchange to a customer premises. The pair of wires can be used to provide telephony as well as data services to the customer premises.
Telephone lines are prone to faults, thus adversely affecting the telephony or data services that may be running over them. Some of these faults are easily identified and rectified, others less so. Typical faults include disconnections, and short circuit between the wires. Various methods have been developed to help identify the faults and propose solutions.
Many methods are based on performing electrical tests on the line, such as measuring the resistance of the line or the AC and DC voltages. These can then be compared to thresholds, and a line may be flagged as faulty if a number of the tests exceed their respective threshold.
US2003/0063712 describes a method for performing the likely location of a fault in a telecommunications system by comparing a test measurement on a line with a reference value and deriving from that comparison the likely location of the fault.
However, such tests are not always accurate, especially when the performance of a line fluctuates and changes over time and during testing. Thus, at the time of testing, the line may appear to perform well, but in the past, there may have been problems.